Optimal Design And Experimental Study Of Foil Gas Thrust Bearing

The dynamic pressure foil bearing is widely used in rotating machinery,which has the advantages of high working speed,small friction and wear,high and low temperature environment adaptability.The difficulty in the research of gas foil bearing is to establish a reasonable foil structure model and solve the Reynolds equation and film thickness equation of gas lubrication accurately.The corrugated foil of the separated hydrodynamic gas thrust foil bearing is a strip structure.The cooling channel in the middle of the adjacent strip corrugated foil can improve the heat transfer capacity of the bearing and reduce the large temperature rise of the bearing during operation.It is very necessary to study the influence of static characteristics of the foil bearing,such as bearing capacity and friction torque,on the structural and operational parameters of the bearing.At the same time,because of its complex structure,it is necessary to design and manufacture the foil thrust bearing with reasonable structure and carry out the experimental research on the bearing performance.In this dissertation,the performance simulation and experimental research of separated air foil thrust bearing are carried out.Firstly,aiming at the structural characteristics of sector flat foil,a triangular unit sheet model is established to solve the deformation of flat foil,which can be used to accurately solve the deformation of flat foil.At the same time,Reynolds equation and film thickness equation of thrust bearing pressure control under steady state in cylindrical coordinate system are established based on gas dynamic lubrication theory.Nonlinear pressure-controlled Reynolds equation and film thickness equation are solved by combining finite element method with finite difference method.The static characteristics of bearing,such as axial bearing capacity and friction moment,are obtained by integrating the film pressure.Secondly,the numerical simulation platform of MATLAB for static characteristics of air foil thrust bearing is established,and the influence laws of structure parameters and operation parameters of air foil thrust bearing on bearing carrying capacity and friction moment are calculated and analyzed.The film thickness at the outlet of air foil thrust bearing,the height of bearing inclined surface,inner and outer radius of bearing,the thickness of bearing flat foil,and so on are analyzed.Influences of Poisson’s ratio of bearing flat foil and running speed on bearing capacity and friction moment of foil thrust bearing.At the same time,the expression of lubricating film thickness of foil thrust bearing in tilted state of rotor thrust plate is established,and the static characteristics of foil thrust bearing when rotor thrust plate is tilted are studied.The results show that when rotor thrust plate is tilted,the bearing capacity and friction moment of air foil thrust bearing will increase,but the distribution of gas film pressure in different segment of bearing is uneven.It will cause severe wear on local bearing blocks.At the same time,according to the influence of structural parameters of air foil thrust bearing on bearing static characteristics,the selection principle of bearing structural parameters is given,the optimum structural parameters of air foil thrust bearing are given,and the static characteristics of air foil thrust bearing under the optimum structural parameters and original structural parameters are analyzed.Corrugated foil was modified to overcome the deformability of inner ring of corrugated foil.Finally,the experimental study on load-bearing performance of separated dynamic pressure gas thrust foil bearing is carried out.Firstly,the composition and function of the test bench are described,the measuring principle of friction moment is introduced,the design and manufacturing process of separated foil thrust bearing is elaborated,the selection of foil material,the structure design of corrugated foil are described.The design of corrugated foil stamping die and the assembly process of bearings are described.The bearing bearing bearing capacity experiments under different conditions are carried out.During the experiment,the bearing capacity reaches 68 N when the speed of turbine rotor is 80 krpm,which reaches the expected bearing capacity.The research results of this dissertation lay a certain foundation for theoretical analysis,design,manufacture and experimental research of separated dynamic pressure gas thrust foil.